$opacity = 0,
           10,
           20,
           40,
           50,
           60,
           70,
           75,
           80,
           90

for oat in $opacity
  .o-{oat}
    opacity (oat/100)


$opactiy-hover = 50,
                 70,
                 80,
                 90

for oth in $opactiy-hover
  .o-hover-{oth}
    opacity 1
    @extend .ease-500
    &:hover
      opacity (oth/100)